For those who want to witness a spectacular event, all you need to do is go outside in May and look up, way up. The newly discovered Comet ATLAS (or C/2019 Y4) will fly by Earth in just a couple of months and experts say that it could be as bright as the moon.
By using the Asteroid Terrestrial-impact Last Alert System (or ATLAS) system that’s based in Hawaii, astronomers discovered the faint comet on December 28, 2019 in the Ursa Major constellation, but in just a few months it has brightened up dramatically. In fact, when it was first noticed back in December, it was near a 20th magnitude which is approximately 398,000 times dimmer than the stars that we can see with the naked eye. Of course, it was around 273 million miles (439 million kilometers) from the sun at that time.
Now mark May 31st on your calendars as the comet will make its closest approach to the sun at a distance of only 23.5 million miles (37.8 million kilometers). This should cause it to increase in brightness by nearly 11 magnitudes meaning that it will be visible by using a small telescope or even a pair of decent binoculars. For comparison, the full moon is normally at 14 magnitudes.
This is incredibly exciting news as those living in the Northern Hemisphere haven’t had a good view of a passing comet in quite some time. In the spring of 1997, Comet Hale-Bopp made a spectacular appearance in the night sky as well as Comet Hyakutake which passed by a year earlier. In March of 2013, Comet PanSTARRS was visible but only in the lower portion of the western sky and immediately after the sun set which made it extremely hard for stargazers to see it. Comets McNaught (in 2007) and Lovejoy (in 2011) also put on great shows but were only seen in the Southern Hemisphere.
Expert John Bortle got his first real look at the Comet ATLAS on March 15th and said, “For the first time in many years I am left at a bit of a loss as to what honestly worthy advice I can offer would-be observers. I really don't know quite what to make of this object,” adding that the head of the comet is big but “very faint and ghostly”. “If it's a truly significant visitor, it should be considerably sharper in appearance. Instead we see, at best, a quite modestly condensed object with only a pinpoint stellar feature near its heart.”
Comet observer Carl Hergenrother weighed in on its brightness by stating, “We should expect the rate of increase to slow again,” adding, “This is where it gets tricky for predicting just how bright it will get.” All we can do is hope that the comet is bright enough for stargazers to capture a glimpse of it while it passes by Earth as we won’t ever see it again because it follows a trajectory of 6,000 years per orbit.
While the Comet ATLAS is currently in Ursa Major, it will travel to the large but faint constellation Camelopardalis (The Giraffe) by March 29th and that’s where it’ll stay through the month of April. It will be located more than halfway up in the north-northwest sky. Hergenrother said it best when he wrote, “It's going to be fun the next few weeks watching Comet ATLAS develop (and provide a nice distraction from the current state of the world).” “Here's to good health and clear skies!”